Manufacture of Multi-Leaf Collimators

Abstract

We propose to shape the leaf by the use of electro-chemical machining (ECM). ECM is a technique by which a blank is suspended within a mould, with a small gap therebetween. A conductive fluid is caused to flow through the gap, and a large electrical current is passed from the mould to the blank. The blank steadily erodes, dissolving into the fluid. The fluid should not provoke a reaction from the material of the blank, such as a surface oxide. Sodium Chloride solution is a common choice. The current that is passed can, if desired, be controlled to a profile that will affect the manner of erosion. Thus, the current profile can be a steady on/off current, or it can be pulsed. One known arrangement is for the current to rise to a peak, then fall to zero, followed by a brief reverse flow.

1 . A method of manufacturing a leaf for a multi-leaf collimator comprising employing an electro-chemical machining technique to produce the leaf. 
   
   
       2 . A method according to  claim 1 , further comprising employing Sodium Chloride solution as a conductive working fluid in the electro-chemical machining technique. 
   
   
       3 . A method according to  claim 1 , further comprising passing a substantially constant current during the electro-chemical machining step. 
   
   
       4 . A method according to  claim 3 , further comprising controlling the current that is passed to a non-linear profile. 
   
   
       5 . A method according to  claim 4 , wherein the non-linear profile is one that rises to a peak. 
   
   
       6 . A method according to  claim 5 , further comprising, subsequent to the peak, reversing the current. 
   
   
       7 . A leaf for a multi-leaf collimator having a shape imparted to it by a process of electro-chemical machining. 
   
   
       8 . A multi-leaf collimator including at least one leaf according to  claim 7 . 
   
   
       9 . A mold for use in electro-chemical machining, comprising a connection for an electrical source, an inlet for a conductive fluid, and an internal shape that corresponds to a desired shape of a multi-leaf collimator. 
   
   
       10 . (canceled) 
   
   
       11 . (canceled)